Antennas are used in various RF (radio frequency) systems. For frequencies up to 60 GHz, antennas are typically designed separately from RFIC chips, and then packaged with the RFIC chips using various techniques. For instance, in millimeter-wave frequencies at 60 GHz up to 94 GHz, an antenna structure can be integrated into an RFIC chip package (antenna-in-package design) by connecting the antenna structure to the RFIC chip using flip-chip bonding or wire bonding techniques, which can improve antenna performance. In particular, with some state of the art technologies, multilayer integrated antenna structures can be fabricated using multilayered printed circuit boards (PCB) (organic-based) or using low temperature co-fired ceramic (LTCC) technology (ceramic-based). These multilayered organic or ceramic integrated antenna structures can be connected to semiconductor IC chips using standard C4 (controlled collapse chip connection) techniques.
Integrated antenna structures that are made with organic or ceramic-based packaging techniques are generally suitable for application operating frequencies in the 60 GHz band while achieving suitable performance. However, for operating frequencies in the 94 GHz band and above, the use of organic or ceramic-based multilayer antenna structures becomes problematic due to, e.g., low PCB and LTCC manufacturing tolerances and resolutions. Moreover, the package materials used for PCB and LTCC technologies are too lossy for such high frequency applications. Moreover, with antenna-in-package designs, the interface (typically flip-chip connection) between the antenna package and the RFIC chip can result in more than 1 dB signal attenuation at 94 GHz, diminishing the advantages of antenna-in-package designs. Thus, it is desirable to design package structures with integrated antennas, which provide high performance for applications with operating frequencies in the 94 GHz band and higher.